Internal or External Insulation

baggote2

Hi. What's people's opinions or experiences on internal or external house insulation. Which to go for, & what width is good or sufficient generally?

heavydawson

baggote2 wrote: »

Hi. What's people's opinions or experiences on internal or external house insulation. Which to go for, & what width is good or sufficient generally?

Depends on what the makeup of the house you're trying to insulate. Can you give a little bit more information on the walls?

MicktheMan

baggote2 wrote: »

Hi. What's people's opinions or experiences on internal or external house insulation. Which to go for, & what width is good or sufficient generally?

EWI (properly detailed) is superior to IWI in every way. Optimum insulation depth is site specific but generally in the greater scheme of things, it doesn't cost a lot more to go with thicker insulation (for example 150 or 200mm instead of 100mm).

bmm

MicktheMan wrote: »

EWI (properly detailed) is superior to IWI in every way. Optimum insulation depth is site specific but generally in the greater scheme of things, it doesn't cost a lot more to go with thicker insulation (for example 150 or 200mm instead of 100mm).

The cost is usually prohibitive though. If you have rooms big enough go with internal.

MicktheMan

bmm wrote: »

The cost is usually prohibitive though. If you have rooms big enough go with internal.

I haven't seen any meaningful cost comparison between the two to comment.
However, I have often heard that ewi is expensive compared to iwi but is it really when you factor in the following:
- moving all internal fixtures and fittings (skirting, curtain poles, sockets, radiators/piping, fitted kitchen / wardrobe / units etc etc
- disruption to occupants (possibly requiring them to move out temporarily renting)
- cost (hidden) of loss of internal floor area
- not to mention the added risk to ones health (and associated cost) by unintended consequences such as interstitial condensation leading to mould growth within the house.

rolisinmarsh

Mostly, It will be depend upon the need of work. Then only we can estimate it's cost also.

D_D

MicktheMan wrote: »

EWI (properly detailed) is superior to IWI in every way. Optimum insulation depth is site specific but generally in the greater scheme of things, it doesn't cost a lot more to go with thicker insulation (for example 150 or 200mm instead of 100mm).

This isn't strictly true, as IWI has some benefits. One being that there is a 'lag' in the time it takes to heat the internal space once heating is turned on for EWI, as the inner leaf 'absorbs' the energy initially before the room can heat up. There is no lag in heating time with IWI. All energy from the heating elements is warming the room from the get go...

This depends on the proposed heating system, but IWI lends itself to a house which is empty for the most part of the day, which needs to be quickly heated once occupied.

EWI lends itself better to a house which is continuously occupied throughout the day.

Just throwing this out there, as it isn't true to say EWI is better than IWI 'in every single way'.

BryanF

D_D wrote: »

This isn't strictly true, as IWI has some benefits. One being that there is a 'lag' in the time it takes to heat the internal space once heating is turned on for EWI, as the inner leaf 'absorbs' the energy initially before the room can heat up. There is no lag in heating time with IWI. All energy from the heating elements is warming the room from the get go...

This depends on the proposed heating system, but IWI lends itself to a house which is empty for the most part of the day, which needs to be quickly heated once occupied.

EWI lends itself better to a house which is continuously occupied throughout the day.

Just throwing this out there, as it isn't true to say EWI is better than IWI 'in every single way'.

Iwi is not continuous as it stops at each internal wall junction/ floor junction- you have thermal bridges sucking out the heat. Therefore you will use more energy.

Iwi may beat up quicker but the reverse is true also - In summer times it contributes to overheating.

In a house you will typically have a routine and will be heating it every day so Ewi makes more sense, any lag becomes less of a problem when you have a timer.

D_D

BryanF wrote: »

Iwi is not continuous as it stops at each internal wall junction/ floor junction- you have thermal bridges sucking out the heat. Therefore you will use more energy.

Iwi may beat up quicker but the reverse is true also - In summer times it contributes to overheating.

In a house you will typically have a routine and will be heating it every day so Ewi makes more sense, any lag becomes less of a problem when you have a timer.

Yep, all true and valid points. EWI should be the way to go when it makes financial sense.

But I was just making the point that for homes which have no set routine, and are unoccupied for long periods of time, and then occupied for short periods requiring to be quickly heated, IWI can be an option. It is one of the few advantages IWI has over over EWI...

BryanF

D_D wrote: »

homes which have no set routine, and are unoccupied for long periods of time, and then occupied for short periods requiring to be quickly heated, IWI can be an option. It is one of the few advantages IWI has over over EWI...

no. there are more likely to experience interstitial condensation and it totally

heavydawson wrote: »

Depends on what the makeup of the house you're trying to insulate.

you don't have these concerns with EWI

D_D

BryanF wrote: »

no. there are more likely to experience interstitial condensation and it totally

you don't have these concerns with EWI

This has no bearing with what I'm saying. What I'm saying is still true. In fact, in a research document which is discussed at length in these forums also states this conclusion;

"One caveat: external wall insulation may not always suit a household with low daytime occupancy. Dry‐lining makes a building thermally ‘lightweight’ and will result in a quicker heating time which could suit a family of commuters. Externally insulating leaves the original thermally ‘heavyweight’ structure exposed to the inside. The best way to heat ‘heavyweight’ structures is to supply constant low‐level heat to them."

You're making an assumption which is misleading. You're saying when EWI is installed, 'and installed correctly' it is better than IWI 'when it is installed incorrectly'. This isn't a fair statement.

With correct consideration and proper design, IWI can be an option for some people.

Ush1

I went with IWI because I am redecorating the whole house section by section and room by room.

It works out cheaper as when I rip out the old plasterboard I simply replace with insulated board.